Chiral reaction products produced from mesogenic molecular structural elements and bifunctionally reactive butanetetraol derivatives, and their use as dopants in liquid crystal phases

Abstract

The new compounds produced from a molecular structural element with two chirality centers and at least one mesogenic structural element are defined by the general formula (I) ##STR1## in which the symbols have the following meaning: Y 1 , Y 2 , Y 3 , Y 4 = in any two cases (a) hydroxy and MC--CO--O or, independently of each other, MC--CO--O and (b), independently of each other (C 1 -C 10 )alkoxy, MC denoting the molecular radical of a mesogenic carboxylic acid after splitting off a COOH group, and it being possible for Y 2 and Y 3 , in the case of (C 1 -C 10 )alkoxy, also to be jointly part of a dioxolane ring, or Y 1 and Y 4 jointly = 0 as part of a tetrahydrofuran ring, and Y 2 and Y 3 = hydroxy and MC--CO--O or, independently of each other, MC--CO--O. Said esters preferably find application as dopants in twistable liquid crystal phases in which they produce temperature compensation and twisting.

We claim: 
     
       1. A compound containing a molecular structural element with two chirality centers and at least one mesogenic molecular structural element, which compound has the formula (I) ##STR13## wherein: two of Y 1 , Y 2 , Y 3  and Y 4  are hydroxy and MC--CO--O, or independently of each other MC--CO--O and the other two of Y 1 , Y 2 , Y 3  and Y 4  are independently of each other (C 1  -C 10 )alkoxy, wherein MC is a mesogenic group of the formula (II)   R--(A.sup.1 --).sub.n1(B--).sub.n2 (A.sup.2 --).sub.n3     (II)     wherein:   R is a straight-chain or branched (C 1  -C 12 )alkyl group, in which one CH 2  group may be replaced by an O atom,   A 1 , A 2  are independently of each other 1,4-phenylene, diazine-2,5-diyl, diazine-3,6-diyl, or 1,4-cyclohexylene, with the proviso that A 1  and A 2  are not both heterocyclic at the same time,   B is CO--O, O--CO, CH 2  --CH 2 , OCH 2  or CH 2  O, and   n1, n2, n3 are independently of each other 0 or 1, n1 and n3 not being 0 at the same time.   
     
     
       2. A twistable liquid crystal mixture containing at least two components, wherein at least one component is a chiral compound of the formula (I) as claimed in claim 1. 
     
     
       3. A liquid crystal mixture as claimed in claim 2 wherein the chiral compound of the formula (I) is present in an amount of from 0.01 to 70% by weight. 
     
     
       4. A compound containing a molecular structural element with two chirality centers and at least one mesogenic molecular structural element, which compound has the formula (I) ##STR14## wherein Y 1  and Y 4  are hydroxy and MC--CO--O, or independently of each other MC--CO--O and Y 2  and Y 3  together form a dioxolane ring, or Y 1  and Y 4  jointly are O and form a tetrahydrofuran ring, and Y 2  and Y 3  are hydroxy and MC--CO--O or, independently of each other, MC--CO--O, wherein MC is a mesogenic group of the formula (II)   R--(A.sup.1 --).sub.n1 (B--).sub.n2 (A.sup.2 --).sub.n3 (II)     wherein:   R is a straight-chain or branched (C 1  -C 12 )alkyl group, in which one CH 2  group may be replaced by an O atom,   A 1 , A 2  are independently of each other 1,4-phenylene, diazine-2,5-diyl, diazine-3,6-diyl, or 1,4-cyclohexylene, with the proviso that A 1  and A 2  are not both heterocyclic at the same time,   B is CO--O, O--CO, CH 2  --CH 2 , OCH 2  or CH 2  O, and   n1, n2, n3 are independently of each other 0 or 1 n1 and n3 not being 0 at the same time.   
     
     
       5. A twistable liquid crystal mixture containing at least two components, wherein at least one component is a chiral compound of the formula (I) as claimed in claim 4. 
     
     
       6. A liquid crystal mixture as claimed in claim 5 wherein the chiral compound of the formula (I) is present in an amount of from 0.01 to 70% by weight. 
     
     
       7. A compound containing a molecular structural element with two chirality centers and at least one mesogenic molecular structural element, which compound has the formula (I) ##STR15## wherein: Y 1  and Y 4  are independently of each other MC--CO--O and Y 2  and Y 3  are independently of each other (C 1  -C 10 )alkoxy, wherein MC is a mesogenic group of the formula (II)   R--(A.sup.1 --).sub.n1 (B--).sub.n2 (A.sup.2 --).sub.n3    (II)     wherein:   R is a straight-chain or branched (C 1  -C 12 )alkyl group, in which one CH 2  group may be replaced by an O atom,   A 1 , A 2  are independently of each other 1,4-phenylene, diazine-2,5-diyl, diazine-3,6-diyl, or 1,4-cyclohexylene, with the proviso that A 1  and A 2  are not both heterocyclic at the same time,   B is CO--O, O--CO, CH 2  --CH 2 , OCH 2  or CH 2  O, and   n1, n2, n3 are independently of each other 0 or 1 n1 and n3 not being 0 at the same time.   
     
     
       8. A twistable liquid crystal mixture containing at least two components, wherein at least one component is a chiral compound of the formula (I) as claimed in claim 7. 
     
     
       9. A liquid crystal mixture as claimed in claim 8 wherein the chiral compound of the formula (I) is present in an amount of from 0.01 to 70% by weight.